Use the "File Association" editor.
KDE Menu -> Control Centre -> KDE Components -> File Associations.
Find the file type in the tree on the right (Probably video files in this case) and edit the "Application preference order" on the far right.
If Xine or any other app is listed twice, delete one. You can also change the pref order or add an app if required.
Edit: beware if deleting an app off the list, that one app name may actually refer to different versions so check first otherwise your new Xine may need to be added again.
Unfortunately you'll have to do this with each individual file type
Click "Apply" when done.
Good Luck.